South African astronomer Sven Bronson discovers that a pair of rogue planets, Bronson Alpha and Bronson Beta, will soon enter the solar system. In eight months, they will pass close enough to cause catastrophic damage to the Earth. Sixteen months later, after swinging around the Sun, Bronson Alpha will return to pulverize the Earth and leave. It is hoped that Bronson Beta will remain and assume a stable orbit.
Wikipedia describes the catastrophic damage from the first pass in the novel as
Tidal waves sweep inland at a height of 750 feet (230 m), volcanic eruptions and earthquakes add to the deadly toll, and the weather runs wild for more than two days. As a token of things to come, Bronson Alpha grazes and destroys the Moon.
Is it known if the authors drew upon the known science of the day to hypothesize what the effects of a planetary near approach would be like? I know it's nearly 100 years ago, but I'm curious how they came up with the science behind the induced tidal waves, and volcanos and earthquakes. The Moon grazing means the approach of at least one of the planets to Earth was less than 400,000 km, so if they'd assumed a mass for the planets, they could estimate quantitatively the forces on the Earth.
The fact that Bronson Alpha and Beta split up and have different, well described orbits suggests they'd certainly put some thought into the orbital mechanics, but I don't know if the orbits are realistic, nor if it was Earth's gravity or the interaction with the Moon that split Alpha and Beta. Is it known to what level of detail they had pursued all of the physics involved in the catastrophic damage and planet trajectories?